Solar updraft tower

The solar updraft tower (SUT) is a renewable-energy power plant for generating electricity from low temperature solar heat. Sunshine heats the air beneath a very wide greenhouse-like roofed collector structure surrounding the central base of a very tall chimney tower. The resulting convection causes a hot air updraft in the tower by the chimney effect . This airflow drives wind turbines placed in the chimney updraft or around the chimney base to produce electricity. Plans for scaled-up versions, such as water extraction or distillation, and agriculture or horticulture.

Commercial investment may have been developed, but it appears to be of special interest in solar retrofit especially in remote areas. A few prototypes have been proposed and proposed for parts of Africa, USA and Australia. An important fact is that solar updraft towers appear to be the only renewable energy technology that can generate electricity from low temperature heat. Functional or mechanical feasibility is not so much an issue now as capitalization. [1]

A comprehensive review of theoretical and experimental aspects of the solar power plant (SUTPP) development is available, with a recommendation for commercial development. [2] A popular update with interview of an informed engineering proponent has been published in National Geographic in 2014. [1]

Design

Power output depends primarily on two factors: collector area and chimney height. A larger area collects and warms a greater volume of air to flow up the chimney; collector areas as large as 7 kilometers (4.3 mi) in diameter have been discussed. A larger chimney height increases the pressure difference via the stack effect ; chimneys as tall as 1,000 meters (3,281 ft) have been discussed. [3]

Heat is stored inside the collector area allowing you to operate 24 hours a day. The ground beneath the solar collector, water in bags or tubes, or a saltwater thermal sink in the collector could add thermal capacity and inertia to the collector. Humidity of the updraft and condensation in the chimney could increase the energy flow of the system. [4] [5]

Turbines with a horizontal axis can be installed in a ring around the base of the tower, as planned for an Australian project and seen in the diagram above; or-as in the prototype in Spain-a single vertical axis turbine can be installed inside the chimney.

A near negligible amount of carbon dioxide is produced as part of operations, while construction materials manufacturing can create emissions. [6] Net energy payback is estimated to be 2-3 years. [5]

Since solar collectors occupy significant amounts of land, deserts and other low-value sites are most likely. In the solar heat collection, the solar collector can be used for the solar array.

A small-scale solar updraft tower may be an attractive option for remote regions in developing countries. [7] [8] The relatively low-tech approach could allow local resources and labor to be used for construction and maintenance.

Locating a tower at high latitudes could produce up to 85 percent of the output of a similar plant located closer to the equator, if the collection area is sloped significantly towards the equator. The sloped collector field, which also functions as a chimney, is built on suitable mountainsides, with a short vertical chimney on the mountaintop to accommodate the vertical axis air turbine. The results shown that solar chimney power plants at high latitudes may have a great performance. [9]

History

A chimney turbine was envisioned as a smoke jack , and illustrated 500 years ago by Leonardo da Vinci . An animal spitted above a fire or in an oven could be turned into a chimney updraft. [1]

In 1896, Mr. Alfred Rosling Bennett published the first patent describing a “Convection Mill” [2] . Even if in the title of the Patent and in the claims the word “Toy” clearly appears and even if in the overall description made inside the Patent it is obvious that the idea was to produce small devices, in page 3 at lines 49-54 Bennett envisions much bigger devices for bigger scale applications. A model of this convection mill, built in 1919 by Albert H. Holmes & Son (London) to demonstrate the phenomenon of convection currents, is on display in the Science Museum, London .

In 1903, Isidoro Cabanyes, a colonel in the Spanish army, proposed a solar chimney power plant in the magazine La energía eléctrica . [10] Another early description was published in 1931 by German author Hanns Günther . [11]Beginning in 1975, Robert E. Lucier applied for patents on a solar chimney electric power generator; between 1978 and 1981 patents (since expired) were granted in Australia, [12] Canada, [13] Israel, [14] and the USA. [15]

In 1926 Professor Bernard Dubos proposed to the French Academy of Sciences the construction of a Solar Aero-Electric Power Plant in North Africa with its solar chimney on the slope of a large mountain. [16] [17] A mountainside updraft tower can also function as a vertical greenhouse. [ quote needed ]

In 1982, small-scale experimental model of a solar tower draft [18] Was built in Manzanares, Ciudad Real , 150 km south of Madrid , Spain at 39 ° 02’34.45 “N 3 ° 15’12.21” W . The power plant operated for approximately eight years. The tower’s guy-wires were not protected against corrosion and failed to rust and storm winds. The tower blew over and was decommissioned in 1989. [19]

Inexpensive materials were used in order to evaluate their performance. The solar tower was built in 1.25 millimeters (0.049 in) thick under the direction of a German engineer, Jörg Schlaich . The project was funded by the German government. [20] [21]

The chimney had a height of 195 meters (640 ft) and a diameter of 10 meters (33 ft) with a collection area (greenhouse) of 46 hectares (110 acres) and a diameter of 244 meters (801 ft), obtaining maximum power output of about 50 kW . Various materials have been used for testing, such as single or double glazing or plastic. One section was used as an actual greenhouse. During its operation, 180 sensors measured inside and outside temperature, humidity and wind speed data were collected on a second-by-second basis. [22] This experiment setup did not sell energy.

In December 2010, Jinshawan in Inner Mongolia , China started operation, producing 200 kilowatts . [23] [24] The 1.38 billion RMB ( USD 208 million) project was started in May 2009. It was intended to cover 277 hectares (680 acres) and produce 27.5 MW by 2013, but had to be scaled back. The solar chimney plant was expected to improve the climate by covering loose sand, restraining sandstorms. [25] Critics have said that the 50m tall tower is as good as it gets to be broken down. [26]

A proposal to construct a solar updraft tower in Fuente el Fresno , Ciudad Real , Spain, Entitled Ciudad Real Torre Solar Would Be the first of icts kind in the European Union [27] and Would stand 750 meters (2,460 ft) tall [28] – Nearly twice as tall as the Belmont TV Mast , qui Was once the tallest structure in the European Union, before being white Shortened by Several hundred feet [29] – covering an area of 350 hectares (860 acres). [30] It is expected to produce 40 MW . [31]

In 2001, EnviroMission [32] proposed to build a solar tower as a solar tower Buronga near Buronga, New South Wales . [33] The company did not complete the project. They have plans for a similar plant in Arizona, [34] and most recently (December 2013) in Texas, [35] but there is no sign of ‘breaking ground’ in any of Enviromission’s proposals.

In December 2011, Hyperion Energy, controlled by Western Australians Tony Sage and Dallas Dempster , Was Reported to be Planning to build a 1-km-tall solar updraft tower near Meekatharra to supply power to Midwest mining projects. [36]

View from the tower on the roof with blackened ground below the collector. One can see the different test materials for canopy cover, and 12 large areas of unblacked ground for agricultural test area.

Based on the need for planning for long-term energy strategies, Botswana ‘s Ministry of Science and Technology designed and built a small-scale research tower. This experiment was run from 7 October to 22 November 2005. It was an inside diameter of 2 meters (6.6 ft) and a height of 22 meters (72 ft), manufactured from glass-reinforced polyester, with an area of ​​approximately 160 square meters ( 1,700 sq ft). The roof was made of a 5 mm thick clear glass supported by a steel framework. [37]

In mid-2008, the Namibian government approved a proposal for the construction of a 400 MW solar chimney called the ‘Greentower’. The tower is planned 1.5 kilometers (4,900 ft) tall and 280 meters (920 ft) in diameter, and the base will consist of a 37 square kilometers (14 sq mi) greenhouse in which cash crops can be grown. [38]

A model solar updraft tower has been constructed in Turkey as a civil engineering project. [39] Functionality and outcomes are obscure. [40] [41]

A second solar collector is operating at the Trakya University in Edirne Turkey and is being used to test various innovations in SUT designs including the ability to recover heat from photovoltaic (PV) arrays. [ quote needed ]

A grade-school pupil’s home do-it-yourself SUT demonstration for a school science fair was constructed and studied in 2012, in a suburban Connecticut setting. [42] [43] With a 7-meter stack and 100 square meter collector, this generated daily average 6.34 mW, from a computer fan to a turbine. Insolation and wind were the major factors on variance (range from 0.12 to 21.78 mW) in output.

Efficiency

The traditional solar updraft tower has a power conversion rate in the solar thermal group of collectors. The low conversion rate is balanced to some extent by the lower cost per square meter of solar collection. [19] [44] [45]

Model calculations estimate that a 100 MW plant would require a 1,000 m tower and a greenhouse of 20 square kilometers (7.7 sq mi). A 200 MW tower with the same tower would require a collector 7 kilometers in diameter (total area of ​​about 38 km²). [5]One 200MW power station will provide enough electricity for around 200,000 typical consumers and will abate over 900,000 tons of greenhouse gases. The glazed collector area is expected to extract about 0.5 percent, or 5 W / m² of 1 kW / m², of the solar energy that falls upon it. If the collector is used collector, the efficiency is doubled. Additional efficiencies are possible by modifying the turbine and chimney design to increase air speed using a venturi configuration. Concentrating thermal (CSP) or photovoltaic (CPV) solar power plants range between 20% to 31.25% efficiency ( dish Stirling). Overall CSP / CPV Efficiency is reduced because collectors do not cover the entire footprint. Without further tests, the accuracy of these calculations is uncertain. [46] Most of the projections of efficiency, costs and yields are calculated theoretically, rather than empirically derived from demonstrations, and are seen in comparison with other collector or solar heat transducing technologies. [47]

An innovative concept recombining a thermal power plant was introduced by Zandian and Ashjaee [48] in 2013 to increase the efficiency of the solar updraft towers. This hybrid cooling-tower-solar-chimney (HCTSC) system was shown to be able to produce an improved power plant compared to the conventional solar power plant like Manzanares, Ciudad Real, with similar geometrical dimensions. In addition, it has been shown that the increase in power output can not be achieved without MW-graded power output without the need for huge individual solar chimney panels. The results showed a maximum of 3 MW power output from the HCTSC system which resulted in a typical 250 MW fossil fuel power plant, with a diameter of only 50 meters (160 ft). The new hybrid design made the solar updraft tower feasible again, and proved to be economical in saving lots of construction cost and time. This concept also recaptures the heat of radiators that are thrown into the atmosphere without efficient use, and prevents generation of excessive greenhouse gases.

The performance of an updraft tower may be degraded by factors such as atmospheric winds, [49] [50] by drag induced by the bracings, [51] and by reflection on the top of the greenhouse canopy.

Related ideas and adaptations

Updraft

The atmospheric vortex proposal [52] replaces the physical chimney by a controlled or ‘anchored’ cyclonic updraft vortex. Depending on the temperature and pressure, or buoyancy, and stability of the vortex, very high-altitude updraft may be achievable. As an alternative to a solar collector, industrial and urban waste heat could be used in the vortex.

Telescopic or retractable gold design may be a very high chimney for maintenance, or to prevent storm damage. Hot-air balloon chimney suspension has also been proposed.

A form of solar boiler technology placed directly above the turbine at the base of the tower could increase the up-draft. [ quote needed ]

Moreno (2006) teaches in US Pat. No. 7,026,723 [53] That a chimney can be economically placed on a hill or mountain slope. Klinkman (2014) in US Patent # 8,823,197 [54]elaborates on constructing diagonal chimneys. A structure as well as a high hoop tunnel, but much longer in a slope. Changing the chimney’s height differential from 200m (the Manzanares experiment) to 2000m (Charleston Peak in Nevada). Increasing the temperature differential between chimney and a factor of ten increases the chimney’s power by one more factor of ten, assuming that the chimney’s walls are engineered to take the extra heat. Concentrating solar heat is often done with reflection.

An inflatable solar chimney power analytically and simulated by computational fluid dynamics (CFD) modeling. This idea has been patented, including the optimal shape of the collector and the analytical profile for the self-inflating tower. [55] The CFD simulation has been evaluated by verification, validation, and uncertainty quantification (VVUQ) of computer simulations by American Society of Mechanical Engineers 2009 standards. [56]

Airtower is a proposal by architect Julian Breinersdorfer to better exploit the high initial capital outlay of building a very high structure by incorporating it into a high rise building core. The proximity of a producer and a consumer can also reduce transmission losses. [57] >

Collector

A saltwater thermal sink in the collector could ‘flatten’ the diurnal variation in energy output, while airflow humidification in the collector and condensation in the updraft could increase the energy flow of the system. [4] [5]

As with other solar technologies, some mechanisms are required. Heat can be stored in heat-absorbing material or saltwater ponds. Electricity can be cached in batteries or other technologies. [58]

A recent innovation has been the use of transpired collectors in place of the traditional glazing covers. [59] Transpired collectors have efficiencies in the 60% to 80% range or 25% efficiency measured with the greenhouse collectors. [60] The large solar collector field can now be reduced A patent has been granted on a solar tower system using transpired collectors. [61]

The Generator

If the chimney updraft is an ionized vortex, then the electro-magnetic field could be tapped for electricity, using the airflow and chimney as a generator. [ quote needed ]

Applications

Air-level release of an atmospheric vortex or solar chimney at altitude could form clouds or precipitation, potentially altering local hydrology. [62] [63] [64] Local de-desertification, or afforestation could be achieved if a regional water cycle was established and sustained in an otherwise arid area.

The solar cyclone distiller [65] could extract atmospheric water by condensation in the updraft of the chimney. This solar cyclonic water distill with a solar collector lays Could adapted the solar collector-chimney system for large-scale desalination of file Managed brine, brackish- or waste-water pooled in the collector base. [66]

Fitted with a chimney scrubber vortex, the updraft could be cleaned of particulate air pollution. Alternately, particulate air pollution caught in the updraft could serve as a nucleation stimulus for precipitation [67] or in the chimney, or at release altitude as cloud seeds .

Energy production, water desalination [66] or simple atmospheric water extraction could be used to support carbon-fixing or food-producing local agriculture, [68] and for intensive aquaculture and horticulture under the solar collector as a greenhouse.

A balloon-suspended lightweight expansible chimney anchored from an urban tether, raised from ground level to low level air to higher altitude. This might improve the quality of the pollution and the cost of major fixed construction.

Airtower is a proposal to improve the capital of the capital. The proximity of a producer and a consumer can also reduce transmission losses. [69]

Capitalization

A solar updraft power station would require a large initial capital outlay, but would have relatively low operating cost. [5]

Capital outlays would be roughly as large as AP-1000 at about $ 5 per Watt of capacity. As with other renewable power sources, you have no need for fuel. Overall costs of operating and interest rates vary from 5 eurocent per kWh for 4% and 20 years to 15 eurocent per kWh for 12% and 40 years. [70]

Estimates of total costs range from 7 (for a 200 MW plant) and 21 (for a 5 MW plant) euro cents per kWh to 25-35 cents per kWh. [71] Levelized cost are approximately 3 Euro cents per KWh for a 100 MW wind or natural gas plant. [72] No actual data are available for a utility scale power plant. [73]